1. Field of the Invention
The present invention relates to systems and methods for transceiving signals, and in particular to a satellite transponder network having integrated redundancy and beamforming/beamswitching capabilities.
2. Description of the Related Art
Satellite transmission systems are well known in the art. One category of such systems use on board transponders that receive signals from one or more ground stations and, with minimal processing (such as frequency translation and amplification), retransmit (transpond) the received signals to other ground stations. Typically, transponders include a plurality of receive antennae communicatively coupled to a plurality of transmit antennae via a switching network.
Because on-orbit servicing of satellite systems is both difficult and prohibitively expensive, the transponders used in such systems are therefore typically designed to provide high reliability and availability.
At the same time, there is a growing need to provide satellite systems with beamswitching and beamforming capabilities. This capability allows transmission of different signals to different geographical areas, and/or adaptive control of transmission signal quality. For example, in areas where rain may degrade the received signal, a beamforming/beamswitching network may be used to strengthen the signal transmitted to such areas.
Traditional switching networks used in such systems offer redundancy or beamforming/beamswitching capability or both, but usually include a vast array of switches, each of which degrade performance, add to cost and complexity, and weight. For example, U.S. Pat. No. 4,626,858 issued to Copeland (which is hereby incorporated by reference herein) uses combiners to merge signals from different beams in a phased array antenna into a single transmission line but does not provide any amplifier redundancy connections. A 6:1 switch is provided to select between different receive beams combinations only, but the switch does not allow selection of both beams and amplifiers.
U.S. Pat. No. 4,868,886 issued to Assal et al. (which is hereby incorporated by reference herein) discloses two designs that focus primarily on beam combining in a phased array in which spare amplifiers are provided (a 6:4 sparing technique is disclosed). However, the system disclosed in Assal operates such that spare amplifiers can only be used in the case of failure of a primary amplifier. The Assal design does not allow all six amplifiers to be used, given sufficient DC power, assuming enough antenna beams were used to utilize this many amplifiers. Assal also discloses a second design in which no redundancy switches or dedicated spare amplifiers are provided, since a matrix type signal combiner is used to share power across the amplifiers. This design can only be used with a multifeed antenna design. What is needed is a system which can be utilized with any multibeam antenna design, and one that allows amplifier sharing.
U.S. Pat. No. 5,132,694 issued to Sreenivas (which is hereby incorporated by reference herein) discloses low level beam forming for a phased array. The system provides dedicated spare amplifiers, however, beam switching is not addressed. The Assal reference teaches using 2-4 backup amplifiers for every 8 active amplifiers required. What is needed is a design that requires no dedicated spare amplifiers and allows the use of every amplifier.
The foregoing designs focus on beam switching as applied to a phased array antenna. All use none, or standard-sparing techniques with dedicated spares. What is needed is a technique that provides combined sparing and beam switching into an integrated ring that also allows any amplifier to be a spare. What is also needed is a design that allows all amplifiers to be used if spacecraft power permits, and is compatible with any multibeam antenna. Furthermore, a system is needed that provides the required redundancy and beamforming/beamswitching capabilities, bit with a minimal number of components. The present invention satisfies that need.